Testing Einstein's Universe

WEEKLY HIGHLIGHTS FOR 7 MAY 2004:

GRAVITY PROBE B MISSION UPDATE

As of Mission Day #17, the Gravity Probe B spacecraft continues to perform
well, and we are expecting a smooth and successful transition into the science
phase of the mission.

The spacecraft remains in a science mission orbit, within the plane of
the Guide Star, IM Pegasi. The gyro readout system performance continues
to exceed
expectations, and all four SQUIDs (Super-conducting Quantum Interference
Devices) are functional and calibrated, with very low noise levels. Power
and thermal
systems meet all of our mission requirements. All spacecraft subsystems continue
to perform nominally.

All four gyros have been electrically suspended in analog mode, and gyros
#1, #2 and #4 are now digitally suspended; we expect gyro #3 to transition
from
analog to digital suspension shortly.

Last weekend, the spacecraft was hit by radiation while passing over the
Earth’s
south magnetic pole. This radiation caused data errors in the spacecraft’s
primary (A-side) computer, which exceeded its capacity for self-correction.
Thus, by design, the spacecraft automatically switched over to the backup
(B-side) computer, placed the spacecraft in a “safe” mode, and
put the planned timeline of events on hold.

The automatic switch over from primary to backup computer worked flawlessly.
The GP-B mission operations team has since re-booted the primary computer,
restored its data parameters, and then commanded the spacecraft to switch
back to the primary computer, which is once again in control. During
this incident,
the GP-B science instrument continued to function perfectly--as expected--with
all four gyros remaining suspended in their assigned modes.

The spacecraft’s Attitude Control System (ATC) is continuing to maintain
a stable attitude (relative position in orbit—pitch, yaw and roll).
However, the process of locking onto the Guide Star, IM Pegasi, has been
delayed a few
days by the South Pole radiation incident.

Overall, at two and a half weeks after launch, it appears that all of the
spacecraft’s
subsystems are continuing to meet or exceed mission requirements, in preparation
for beginning the science experiment.

The spacecraft
is being controlled from the Gravity Probe B Mission Operations Center, located
here at Stanford University. Mission operations have demonstrated that the
hardware developed for the GP-B mission is functioning as planned, and the
Stanford-NASA/MSFC-Lockheed
Martin operations team is continuing to perform superbly.

Please Note: During the Initialization & Oribit Checkout
(IOC) Phase of the GP-B mission, we will update this Web site and send out
an email update once a week (usually on Thursday or Friday) to keep you appraised
of our progress.
From time to time, we may post and email extra updates, as warranted by mission
events.

FOLLOW IOC ACTIVITIES AND LEARN MORE ABOUT GRAVITY PROBE B

If you are interested in following the IOC procedures more closely, you'll find
a schedule and description of them on pages 12-14 of the Gravity Probe
B Launch Companion. This document also provides an overview and explanation
of the Gravity Probe B experiment and information about the spacecraft and
GP-B's amazing technologies. Click
here to download the GP-B Launch Companion in Adobe Acrobat PDF format.
(Please note: this file is 1.6 MB, so it may take awhile to download if you
have a
slow Internet connection.)

Photos: The first photo, showing the Delta II rocket and
payload lifting off of the launch pad was taken by photographer Bill Hartenstein
(http://www.ktb.net/~billmeco)
. The second photo—actually three photos electronically "stitched
together"— was taken by Marian Chuang, a systems enginee at Lockheed Martin
Missles & Space Corporation. Tthe photo showing
the spacecraft separating from the second stage rocket was extracted from
NASA KSC's launch video. The final "photo" is actually a drawing
of the GP-B spacecraft on orbit, as depicted in an animation created by NASA's
Marshall
Space Flight Center. Click on the thumbnails to view enlarged copies of these
photos.

FOLLOWING THE GP-B MISSION ON THE WEB

In addition to this Web site, here are some other Web sites that have
information, photos, and video of the GP-B launch and mission.

The ELV
Missions Virtual Launch Center Web page on the John F. Kennedy Space
Center Web site has information and several streaming video clips covering
the GP-B mission.
(You can view these video clips free of charge, but you will need to have either
the Real Media Player or Windows Media Player installed on your computer to
view them.)

NASA's Marshall Space Flight Center Gravity
Probe B.com Web page has a number
of great photos from the GP-B launch, including photos of the spacecraft
separation, as well as other information about Gravity Probe B.

The Science @ NASA Web
site, hosted by NASA's Marshall Space Flight Center, posts several stories
each month about scientific research projects in which
NASA is involved. This site currently features two general interest stories
about Gravity Probe B: In
search of Gravitomagnetism and A
Pocket of Near Perfection. (In addition to the Web versions, these stories
are also available in both plain text and streaming audio formats.)

Another very comprehensive source of information about the GP-B launch
is the Spaceflight
Now Web site. This site contains an excellent photo gallery, as well
as a number of Quicktime video clips of the launch. However, you have to
become
a subscriber to this
site ($$$) in order to view the video clips.

On Tuesday, April 13,2004, Gravity Probe B was the lead story in the Science
section of the New
York Times, and
it was one of the front page stories in the San
Jose Mercury News. (You'll need to
register on the Web sites of these newspapers to view these stories online.) In
addition, a story about GP-B appeared on the New
Scientist Web on April 13, 2004.

The official pre-launch Gravity Probe B mission and science briefing was
held on Friday, April 2, 2004 at 1:00 PM Eastern Daylight Time at
NASA Headquarters in Washington, D.C.
The participants in the briefing (pictured from left to right in the photo)
were:

RECEIVE GRAVITY PROBE B WEEKLY HIGHLIGHTS BY EMAIL

If you are interested in automatically receiving these weekly highlights
and other important GP-B mission information by email, you can subscribe to
our Gravity Probe B Update email list by sending an email message to "majordomo@lists.Stanford.edu" with
the command "subscribe gpb-update" in the body of the message (not
in the Subject line). You can unsubscribe from this mailing list at any time
by sending an email message to the same address with the command, "unsubscribe
gpb-update" in the body of the message.